Apparatus, system and method for use in determining a property of a flowing multiphase fluid

ABSTRACT

An apparatus, system, and method for use in determining at least one property of a flowing multiphase fluid involves comparing an initial signal and a pair of local reference signals with a set of flow characteristics extracted from reference sensor feature maps wherein the signals are related to the flow of the multiphase fluid as it passes through a flow passage which is continuously monitored, adjusted, and calibrated. Based upon the comparison, a decision is made to either resume monitoring of the flowing multiphase fluid by using a pair of local reference signals which are closely positioned and defined, or to adjust the flow passage area significantly in order to improve metering flow conditions. The invention is best suited for determining transport flow velocity and gas void fraction or relative proportions of the gas phase and the liquid phase within the multiphase fluid which subsequently can be used to quantify gas and liquid flowrates.

TECHNICAL FIELD

The present invention relates to an apparatus, system, and method foruse in determining a property of a flowing multiphase fluid.

BACKGROUND OF THE INVENTION

A multiphase fluid is a fluid having more than one phase, such as afluid having two or more liquid phases or a combination of a gas phasewith one or more liquid phases. Flowing multiphase fluids are frequentlyencountered in industry and it is often necessary or desirable to havethe ability to determine their flowing properties as well as flowratesof individual fluids. Unfortunately, however, determining the flowingproperties of a multiphase fluid can be difficult for various reasons.Gravity leading to local phase separations, inertia leading to flowdetachment and phase separation, and interfacial friction, as well asnon-equilibrium gas exholution phenomena occurring within the body of ametering device, affect the ability to obtain reliable and consistentmeasurements of the flowing properties of multiphase fluids when singlephase fluid measurement apparatus and techniques are used.

As a result, there are several conventional approaches to determiningthe flowing properties of multiphase fluids. For example, some effortshave used Bernoulli's equation to determine the mass flowrate of amultiphase fluid by measuring pressure differentials between differentlocations in a relatively long conduit. Other efforts involve directphase density metering which uses a concentrated beam of a specifiedradiation wavelength exhibiting a specific absorption coefficient foreach phase. Various other problems arising with conventional meteringdevices and methods may include limited application for a specific gasand liquid flow range; gas exholution (indicated as gas previouslydissolved in liquid being released in the body of the metering device)leading to errors in calculating densities of the phases due tonon-equilibrium gas-liquid dissolution; and ineffectiveness orinaccuracies in determining flow characteristics of each of the gas andliquid phases.

Pipe transportation of a multiphase fluid is typically encountered inthe oil and gas industry and power systems handling vapors andcondensate. The current method for measuring the total (gas and liquid)transported flowrate and phase ratios of a multiphase fluid involvesinitially separating the phases using a separator tank, and thenmetering each separated phase individually. However, this method doesnot provide real-time, continuous information on flowrates and phaseratios of simultaneously produced oil, gas, and water originating fromnumerous wells. Typically, produced fluids (i.e., gas and liquid) fromonly a single well at a time are directed to the separator tank, whileproduced fluids from other wells must bypass the separator tank to bedirected to the field main fluid collector system. Accordingly, there isa need in the art for improved apparatus and methods of mitigating theseproblems.

SUMMARY OF THE INVENTION

The present invention relates to an apparatus, system, and method foruse in determining at least one property of a flowing multiphase fluidby comparing an initial signal and a pair of local reference signalswith a set of reference sensor maps, wherein the signals are related tothe flow of the multiphase fluid as it passes through a flow passagewhich is continuously monitored, adjusted, and tailored. Based upon thecomparison, a decision is made to either resume monitoring of theflowing multiphase fluid by using a pair of local reference signalsobtained from two well defined, consecutive, flow passage minor areaadjustments or by significantly changing the flow passage area to attainthe desired metering flow conditions. The invention is best suited fordetermining transport flow velocity and gas void fraction or relativeproportions of the gas phase and the liquid phase within the multiphasefluid and subsequently gas and liquid flowrates. It was surprisinglydiscovered that by conducting the method of the present invention, oneor more of the following benefits may be realized:

-   -   (1) Compared to conventional flow metering methods, the        invention does not require use of a separator tank to separate        the phases before metering, and provides real-time, continuous,        on-line monitoring and metering to determine a property of the        flowing multiphase fluid.    -   (2) In the method form of the invention, it can be determined        whether an initial measurement of a property of the flowing        multiphase fluid lies in a suitable metering condition by        obtaining a set of corresponding measurements for a pair of        local metered references for comparative assessment. The local        reference metered conditions are set by slightly altering the        metering area by finely adjusting the position of a movable flow        diverter within the metering flow area from its “home” position        to positions proximate the “home” position, such that the “home”        position is median between the local positions or coincides with        one of the pair positions. Although the metering flow area        (hence, gas-liquid transport velocity) may be slightly altered,        the composition of the multiphase fluid and its flowrate are        only negligibly altered. In contrast, conventional flow control        valves operate between only “fully open” or “fully closed”        positions to change the flowrate and input-output pressure drop,        and use set point values to maintain a target flowrate. This        invention thus does not equate to a conventional flow control        valve since the purpose of moving the flow diverter in the        optimal measurement zone is not to alter the flow rate.    -   (3) The measurements are validated and determined to be        acceptable by comparison with a set of sensor feature maps. The        set of sensor feature maps preferably comprises at least one        sensor feature map representing each signal as a function of the        property of the flowing multiphase fluid which is to be        determined. Where the method includes the steps of deriving        parameters from the signals, the set of sensor feature maps        preferably comprises at least one sensor feature map for each        parameter as a function of the property of the flowing        multiphase fluid which is to be determined. The set of sensor        feature maps may also comprise a set of graphs or correspondent        analytical equations in which the property is expressed either        as a function of the signal or of a parameter derived from the        signal. If it is determined that the measurements are        acceptable, metering is maintained at such established metering        conditions as long as the input flow conditions do not        significantly change. If it is determined that the measurements        are unacceptable, a “search” is triggered for better metering        flow conditions, assessed by a second pair of local reference        positions of the movable flow diverter. The metering flow area        is changed significantly by sizably displacing the movable flow        diverter to a “new” home position. Through successive repeated        pair measurements, the metering flow area can be precisely        adjusted to maintain suitable metering conditions.    -   (4) Although the total amount of time for metering at one        position is short (about 10 seconds to about 60 seconds),        measurable parameters and sufficient data are generated.    -   (5) Using the method form of the present invention, it can be        determined whether the fluid may include only a gas phase or        only a liquid phase, or both. If the fluid includes only a gas        phase or only a liquid phase, subsequent metering tasks are        performed using conventional, single-phase integrated metering        techniques well known to those skilled in the art.    -   (6) In one embodiment of an apparatus form of the invention, the        body of the apparatus is substantially Y-shaped. By having a        substantially Y-shaped cross section, the multiphase fluid flows        smoothly as it is directed vertically into the entrance, through        the flow passage, and is discharged horizontally from the flow        passage through the exit. The Y-shape of the body and the        combination of the conical shape of the movable flow diverter        and tapered shape of the stationary housing allow for a gradual        transition of gas-liquid from the inlet upwardly and vertically        to exit horizontally, thus facilitating smooth flow of the        multiphase fluid, thereby avoiding phase separation and        re-circulation conditions by preventing excessive velocity        changes, and particularly fluid pressure changes.

Thus, broadly stated, in one aspect of the invention, a method fordetermining a property of a flowing multiphase fluid is provided,comprising:

(a) directing the multiphase fluid through an apparatus comprising:

-   -   a body comprising an entrance for directing the multiphase        fluid, and an exit for discharging the multiphase fluid and        defining a flow passage between the entrance and the exit for        directing the flow of the multiphase fluid therethrough; and    -   a flow diverter assembly comprising a stationary housing        disposed downstream of the entrance; and a movable flow diverter        movable towards, within, or away from the stationary housing;        the stationary housing and the movable flow diverter together        defining a metering flow area and guiding the flow of the        multiphase fluid towards and out of the metering area;

(b) positioning the movable flow diverter at a home position;

(c) monitoring the multiphase fluid with at least one monitoring devicein communication with the metering flow area to obtain a signalrepresenting the property of the multiphase fluid;

(d) determining a value of the property of the multiphase fluid bycomparing the signal with a set of sensor feature maps;

(e) adjusting the movable flow diverter by predetermined incrementsproximate to the home position to obtain a first pair of referencesignals, and comparing the reference signals with the set of sensorfeature maps to determine values of the property of the multiphasefluid;

(f) comparing the value obtained in step (d) with the values obtained instep (e); and

(g) based on the comparison, continuously monitoring the multiphasefluid, or re-adjusting the position of the movable flow diverter withinor away from the stationary housing to obtain a new home position andsuitable metering conditions in the metering area.

In another aspect of the invention, a system for use in determining aproperty of a flowing multiphase fluid is provided, comprising:

(a) an apparatus comprising:

-   -   (i) a body comprising an entrance for directing the multiphase        fluid, and an exit for discharging the multiphase fluid and        defining a flow passage between the entrance and the exit for        directing flow of the multiphase fluid therethrough;    -   (ii) a flow diverter assembly comprising a stationary housing        disposed downstream of the entrance; and a movable flow diverter        movable towards, within, or away from the stationary housing;        the stationary housing and the movable flow diverter together        defining a metering flow area and guiding the flow of the        multiphase fluid towards and out of the metering area; the        movable flow diverter being coupled to a displacement assembly        for positioning the flow diverter towards, within, or away from        the stationary housing;    -   (iii) at least one monitoring device mounted in fluid        communication at a measurement point for monitoring the property        of the multiphase fluid flowing therethrough; and

(b) a controller communicatively coupled to the at least one monitoringdevice for calculating the property of the multiphase fluid from atleast two signals received from the at least one monitoring device.

In yet another aspect of the invention, an apparatus for use indetermining a property of a flowing multiphase fluid is provided,comprising:

(i) a body comprising an entrance for directing the multiphase fluid,and an exit for discharging the multiphase fluid and defining a flowpassage between the entrance and the exit for directing flow of themultiphase fluid therethrough;

(ii) a flow diverter assembly comprising a stationary housing disposeddownstream of the entrance; and a movable flow diverter movable towards,within, or away from the stationary housing; the stationary housing andthe movable flow diverter together defining a metering flow area andguiding the flow of the multiphase fluid towards and out of the meteringarea; the movable flow diverter being coupled to a displacement assemblyfor positioning the flow diverter towards, within, or away from thestationary housing;

(iii) at least one monitoring device mounted in fluid communication at ameasurement point for monitoring the property of the multiphase fluidflowing therethrough;

wherein the apparatus is capable of being communicatively coupled to acontroller for calculating the property of the multiphase fluid from asignal received from the at least one monitoring device.

Additional aspects and advantages of the present invention will beapparent in view of the description, which follows. It should beunderstood, however, that the detailed description and the specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described with reference to theaccompanying drawings, in which:

FIG. 1 is a schematic view of a preferred embodiment of a system form ofthe invention.

FIG. 2 is a block diagram of the system of FIG. 1, showing operations ofeach component of the system.

FIG. 3 is a schematic view of a preferred embodiment of an apparatusform of the invention.

FIG. 4 is a block diagram showing a preferred embodiment of a methodform of the invention.

FIG. 5 is a schematic view of one embodiment of a flow diverter assemblycomprising a stationary housing and a movable flow diverter defining themetering section (left), and a flow area diagram for a selected position(xi=80 mm) of the movable flow diverter and for calculating pressuredrop (right).

FIG. 6A is an example of a simplified double-cone flow model (right)obtained from an actual flow diagram for a flow diverter assembly and aselected position (xi) of the movable flow diverter (left), suggesting aminimum value of flow area at a level specific to the position of themovable flow diverter and a contraction-expansion of flow area assimplified by the model. The model may be used for calculating thenon-recoverable pressure drop as exemplified in FIG. 6B and explained inExample 1.

FIG. 6B (right) is an example of a graph prepared for use in theinvention, in which non-recovered pressure loss across the movable andstationary flow diverters is calculated for various positions (xi) ofthe movable flow diverter (and implicitly of the value and position ofminimum flow area illustrated by the simplified double-cone flow areamodel), as evaluated using both “Crane” and “Wade-Owen” calculationmodels (Example 1). The double-cone simplified flow model (FIG. 6B,left) was used to determine the non-recovery pressure drop for a certaingas and liquid flowrates (FIG. 6B, right, MEDALLION) at variouspositions of the movable flow diverter (xi).

FIG. 7 is an example of a graph extracted from the sensor feature mapsand prepared for use in the invention, in which PDF signal modificationsare shown as being related to the dimensionless metered velocity Um (thespecific sensor feature map being extracted as PDF=F(Um) for GVF=0.4).FIG. 7 also presents in medallion the analytical equation obtainedthrough regression of the same.

FIGS. 8A-B are 3-D examples of an acceleration sensor feature map andthe respective PDF contour map (B)—a graph prepared for use in theinvention using dimensionless transport velocity (Um) as well as PDF andGVF. The maps use a great number of sensor-response experimental data.

FIG. 9 is an example of a graph extracted from the sensor feature mapsthrough a metering simulation procedure using two transport velocities(Example 2) for use in the invention, in which PDF signal modifications(PDF1, PDF2) with two simulated measurements performed for a simulatedsmall displacement of movable flow diverter (x1, x2) are illustrated toclarify the procedure used for determining the actual transport velocityUm.

FIG. 10A is an example of a graph extracted from the sensor feature mapsfor use in the invention, in which PDF=F(Um) for GVF=0.2, 0.4 and 0.8and the measured PDF for two pair metering locations as x1=85 mm (homeposition) and x2=86 mm (“nearby”).

FIG. 10B is an example of a graph detailing a zone of interest from FIG.10A for use in the invention, in which details indicating the specific“Velocity Slope” points of calculations using potential Um solutions inwhich PDF=F(Um) for GVF's=0.2 and 0.4 are shown.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention relates to an apparatus, system, and method foruse in determining a property of a flowing multiphase fluid. Preferably,however, the multiphase fluid includes a gas phase and at least oneliquid phase. Most preferably, the multiphase fluid is a two phase fluidcomprising a gas phase and a liquid phase. As used herein, “phase”refers to a substance having a chemical composition and physical statethat is distinguishable from a co-currently flowing phase of a fluidhaving a different chemical composition or a different physical state.The invention is ideally suited for use with two phase multiphasefluids, but may also be used with single phase fluids and multiphasefluids having more than two phases.

The method may be used to determine any property of a flowing multiphasefluid, including density, volumetric flowrate, mass flowrate, andrelative composition of the various phases of the multiphase fluid.Preferably, however, the method is used to determine the totaltransported volumetric flowrate and relative proportions of the phasespresent in the multiphase fluid. Most preferably, the method is used todetermine the total transport flowrate and the relative proportions ofgas and liquid phases that are present in a two phase multiphase fluid.In one embodiment, the method is used to determine the total transportflowrate expressed as total transport velocity (“U_(m)”), and therelative proportions of the gas versus total gas and liquid transportedexpressed as gas void fraction or void fraction (“GVF”).

Referring to FIGS. 1-4, the system form of the invention includes anapparatus (10) and a controller (12) generally comprising a data andstatistics processing module (14), a sensor feature map module (16), anda flow area adjustment module (18), all of which intercommunicate toperform selected functions as detailed in FIGS. 2 and 4.

An exemplary apparatus (10) which can be used in the present inventionis shown generally in FIG. 3 to include a body (20) which is hollow anddefines an entrance (22), an exit (24), a flanged end (26), and a flowpassage (28) extending and defining a fluid flow path through the body(20) connecting the entrance (22) and the exit (24).

The body (20) allows the multiphase fluid to flow smoothly from atransport line (not shown) into the entrance (22), through the flowpassage (28), and out the exit (24) to return into the transport line(not shown). Preferably, the body (20) has an inner diameter which isthe same or approximates the inner diameter of the transport line (notshown) from which the multiphase fluid enters into the apparatus (10)through the entrance (22), and into which the multiphase fluid isdischarged from the apparatus (10) through the exit (24).

In one embodiment, the body (20) is substantially Y-shaped. By having asubstantially Y-shaped cross section, the multiphase fluid flowssmoothly as it is directed vertically into the entrance (22), throughthe flow passage (28), and is discharged horizontally from the flowpassage (28) through the exit (24).

In one embodiment, the body (20) is substantially elbow-shaped. Theelbow shape is rendered by inclusion of either a separating diaphragm(43) or a filling material (not shown) at the flanged end (26). Theseparating diaphragm (43) or the filling material (not shown) allow forlow friction movement of a movable flow diverter (48). By having asubstantially elbow-shaped cross section, the potential for accumulationof the light phase or gas in the “dead zone” at the flanged end (26) maybe avoided.

A flow diverter assembly comprises a stationary flow conditioninghousing (32) and a movable flow diverter (48). The stationary flowconditioning housing (32) and the movable flow diverter (48) operate intandem and co-axially to modify a metering section (30) as the movableflow diverter (48) is moved towards, within, or away from the stationaryhousing (32). The stationary flow conditioning housing (32) and themovable flow diverter (48) together guide the flow of the multiphasefluid towards and out of the metering section (30). As will be furtherdescribed, the configurations of the stationary flow conditioninghousing (32) and the movable flow diverter (48) enable one or more ofthe following:

-   -   establish a desired, predetermined flow metering section (30);    -   handle a relatively broad range of gas-liquid ratios and        transport velocities at the entrance (22) and adjustment of the        flow metering section (30) to obtain accurate measurements with        negligible modifications of inlet gas-liquid GVF at each        metering position during the standard metering procedure which        involves minor modifications of metering area executed through        small displacements of the movable flow diverter around a        specific home position;    -   facilitate the flow area transition from circular at the        apparatus entrance (22) to annular within the metering section        (30) and circular at the exit of the metering section (30);    -   eliminate flow oscillations occurring during some critical input        flow conditions due to gas-liquid flow pattern transitional        conditions known as “flow pattern transitional zones.” Such flow        oscillations may induce noise unrelated to gas-liquid transport        velocity and concentration that may be picked up by the        monitoring device; and    -   minimize the non-recoverable pressure drop calculated for a pair        of metering positions of the movable flow diverter (48).        Consequently, the flowrate and gas-liquid distribution are        relatively unchanged between two operations that represent the        designated pair metering procedure.

The stationary flow conditioning housing (32) is disposed downstream ofthe entrance (22), and includes a converging inlet (34) and a divergingoutlet (36) at the opposite ends thereof, and a metering section (30)between the converging inlet (34) and the diverging outlet (36). Thehousing (32) defines the metering section (30) at which properties ofthe flowing multiphase fluid are measured and within which the flowconditions may be adjusted, as will be further described. The housing(32) may be formed by one or more structures which are contoured toadapt to a broad range of inlet (22) transport velocities (Um) andgas-liquid ratios (GVF), and to eliminate the risk of inducingseparation-detachment flowing conditions throughout the flow passage(28).

In one embodiment, the housing (32) is formed by a pair ofdouble-tapered inserts (40) which are attached to the inner surface (42)of the body (20). Rapid velocities-pressure variations inside the flowdiverter system which may lead to fluid detachment, gas exholution, andnon-equilibrium related gas-liquid “noise” are avoided through thedesign of double-tapered inserts (40) and of the movable flow diverter(48) as well as through the metering controlling concept. The velocitymay then slightly decrease as the multiphase fluid passes from themetering section (30) within which the flow is controlled by the inserts(40) and the movable flow diverter (48), into the outlet (36) and flowpassage (28). As will be further described, the position of the movableflow diverter (48) in conjunction with the inserts (40) “conditions” theflow of the multiphase fluid for the desired or suitable meteringconditions.

However, in the present invention, the velocity of the multiphase fluidat the metering section (30) is variable, and may be precisely adjustedto achieve the desired or suitable metering conditions. The movable flowdiverter (48) is positioned towards, within, or away from the stationaryflow conditioning housing (32), and is configured to be axially movablewithin the body (20), particularly within the double-tapered inserts(40), in order to adjust the transported velocity of the multiphasefluid entering the metering section (30). The transported fluid velocitymay be altered by adjusting the position of the movable flow diverter(48) at relatively small distances such that the recoverable pressuredrop of the apparatus and input flowrate and gas-liquid proportion (GVF)are not noticeably changed during a pair metering procedure, or insignificantly larger distances to influence the inlet flowrate of themultiphase fluid. The movable flow diverter (48) is coupled to adisplacement assembly (46) for calibrating and adjusting the position ofthe movable flow diverter (48) towards and away from the housing (32).

In one embodiment, the movable flow diverter (48) comprises a plugpositioned on a rod (50) that is disposed centrally and extends throughthe flanged end (26) to connect to the displacement assembly (46). Inone embodiment, the movable flow diverter (48) is substantiallyconically-shaped. The conical shape streamlines the upward incoming flowof gas and liquid, avoiding fluid detachment and related unwantedgas-liquid separation activities to take place upstream or downstreamthe metering section (30).

In one embodiment, the body (20) is substantially Y-shaped and themovable flow diverter (48) is substantially conical-shaped. Having aY-shaped-body (20) and a conical-shaped flow diverter (48) conditionsthe incoming multiphase fluid into a higher suitable velocity, achievinga quasi-homogenous mixture of gas-liquid in the metering section (30) byfacilitating smooth flow of the multiphase fluid, thereby avoiding fluidseparation, re-circulation conditions, significant velocity changes,leading to downstream flow constrictions such as vena contracta, and anincrease in any non-recovered pressure drop. As used herein, the term“homogenous” refers to a gas and liquid as well as to two liquids (e.g.,gas and oil; air and water, or oil and water only) behaving almost as asingle, well-mixed phase. The housing (32) enables a smooth velocitychange and minimizes the total pressure loss of the multiphase fluidacross the entrance (22) and exit (24) of the apparatus (10), whileachieving a quasi-homogenous mixing at the metering section (30).

The displacement assembly (46) is positioned outside of the flanged end(26) of the body (20) and adjacent to the exit (24). The displacementassembly (46) includes a flow diverter positioner (52) and a motor (54),each of which is in communication with the controller (12) by respectivecommunication lines (56 a, 56 b). In one embodiment, the flow diverterpositioner (52) comprises an impulse-type stepwise displacement device.In one embodiment, the motor (54) comprises a linear stepper motor.

All possible transport velocity changes in the metering section (30) andsubsequent flowrate of the multiphase fluid are mediated by thecorresponding various positions of the movable flow diverter (48). Thelinear stepper motor (54) produces incremental or decremental linearmovement, namely movement occurring in steps of precise distance (58).The position of the movable flow diverter (48) may be represented bydistance “x” which varies between a minimum distance “x₁” to a maximumdistance “x₂” (FIG. 3).

At any particular “x_(i)” position of the movable flow diverter (48), amaximum flow area and minimum multiphase fluid velocity is observed at adistance x_(i) (depending on the particular design of the moveable flowdiverter (48) and housing (32)). When the movable flow diverter (48) isretracted well away from the housing (32) at the divider (43), themetered area (30) is mainly identical with the minimum area determinedby the particular design of the housing (32).

The positioner (52) continuously records the position of the movableflow diverter (48) in real-time, and generates a signal representativeof the position of the movable flow diverter (48). The signal istransmitted through the communication line (56 a) to the controller(12). The controller (12) is responsive to the positioner (52) and motor(54), and produces output signals to the motor (54) throughcommunication line (56 b) to impart one of the following actions: (i) nomovement of the movable flow diverter (48); (ii) fine back-and-forthmovement of the movable flow diverter (48) over a relatively smalldistance to evaluate a pair of local flow diverter positions (andimplicitly of metered flow area and transport velocity U(m)); and (iii)changing the location of the movable flow diverter (48) over asubstantially larger distance to conduct a “search” for a suitablemetering flow area within the metering section (30), as will be furtherdescribed. The motor (54) thus receives signals from the controller (12)to advance or retract the movable flow diverter (48) towards or awayfrom the housing (32).

The controller (12) may also receive and be responsive to signalsreceived from various monitoring devices (64, 66, 68, 72), all of whichare communicatively coupled with the controller (12) by respectivecommunication lines (56 c, 56 d, 56 e, 56 f). As used herein, the term“communicatively coupled” is intended to mean either a direct or anindirect communication connection. Such connection may be a wired orwireless connection which is well known to those skilled in the art andwill therefore not be discussed in detail. Each monitoring device (64,66, 68, 72) detects a parameter of interest and generates signalsrepresentative of the parameter in continuous real time. The signals arethen transmitted to the controller (12) for processing and analysis, andin the appropriate circumstances, for generating output signals tocontrol the positioner (52) and motor (54).

The monitoring devices (64, 66, 68, 72) are mounted in fluidcommunication (i.e., in contact with the fluid) at measurement pointsfor monitoring properties of the multiphase fluid. The measurementpoints may be anywhere along the flow passage (28). Preferably, themeasurement points may include the entrance (22), the housing (32), andthe exit (24), and the tip (60) of the movable flow diverter (48).Preferably, the monitoring devices (64, 66, 68, 72) do not impede theflow of the multiphase fluid. The monitoring devices (64, 66, 68, 72)are coupled to corresponding ports (62 a, 62 b, 62 c, 62 d, 62 e)provided at the measurement points to enable contact with the multiphasefluid. In one embodiment, the ports (62 a, 62 e) are disposed circularlywithin the metering section (30). In one embodiment, a port (62 b) ispositioned at the tip (60) of the movable flow diverter (48).

The monitoring devices (64, 66, 68, 72) may comprise any types oftransducers capable of generating signals representing properties of theflowing multiphase fluid. Suitable transducers include, but are notlimited to, accelerometers, pressure transducers, differential pressuretransducers, and temperature transducers. Preferably, the generatedsignals are electrical signals.

Pressure measurement points may be used for continuously monitoringpressure changes occurring as the multiphase fluid flows through theapparatus (10). In one embodiment, a measuring port (62 a) is positionedat the metering section (30) as dictated by the relative positions ofthe inserts (40). In one embodiment, a measuring port (62 b) ispositioned at the tip (60) of the movable flow diverter (48) positionedin the vicinity of the metering section (30). The continuous pressurevariation may be made with a transducer (64) which is in contact withthe multiphase fluid through the measuring ports (62 a, 62 b), andprovides a voltage reading of the multiphase fluid at a particularlocation dependent on the configuration of the flow diverter (48) andhousing (32), or at the tip (60) of the flow diverter (48).

The passage of the multiphase fluid through the metering section (30)produces a relatively small acceleration-related pressure fluctuationdefined as:ΔP _(acc)=Δρ_(m) ·U _(m)·Δ(U _(m))  Eq. (1)wherein the symbol Δ indicates time or local position change orfluctuation (of transport velocity and/or density), P_(acc) is theacceleration component of pressure, ρ_(m) is the composite gas-liquidlocal density, and U_(m) is the local transport velocity. “Local”indicates a variable value in the metering area (30), where, usually,the acceleration sensor is placed.

However, as described in U.S. Pat. No. 6,155,102 to Toma et al.,acceleration-related pressure drop fluctuation impulses may be useful indetermining a property of a multiphase fluid.

In one embodiment, the transducer (64) is a high-frequency accelerationsensor capable of detecting real-time pressure oscillations mainlycaused by density variations of the multiphase liquid flowing throughthe metering section (30). The pressure oscillations are transmitted inthe form of signals through the communication line (56 c) to thecontroller (12). The controller (12) processes the signals and convertsthem into voltage oscillations representative of the passage through themetering area of the two distinct phases of the multiphase fluid.

A pair of pressure measurement points may be provided at the entrance(22) and the metering section (30) to define a pressure differentialwhich is detected by a differential pressure transducer (66) connectedbetween metering ports 62 c and 62 d. A pressure measuring port (62 c)is provided to measure the pressure at the entrance (22), and isconnected to a pressure transducer (68) to provide a pressure reading.The pressure readings are transmitted in the form of signals throughrespective communication lines (56 d, 56 e) to the controller (12) whichprocesses the signals. In one embodiment, a pair of pressure measurementpoints may be provided at the entrance (22) and the exit (24) to definea pressure differential. The pressure changes approximate the respectiveflow rates of the phases of the multiphase fluid. By determining theindividual flow rates of the gas and of the liquid phases of themultiphase fluid, the composition of the multiphase liquid (i.e., theratio of the gas to the total gas and liquid phases) can be accuratelydetermined.

In one embodiment, the exit (24) may be provided with a temperature port(62 e). A temperature measurement may be made with a temperaturetransducer (72) which is in contact with the multiphase fluid through athermowell mounted at port (62 e), and provides a continuous temperaturereading of the multiphase fluid before it is discharged through the exit(24). The temperature reading is transmitted in the form of a signalthrough the communication line (56 f) to the controller (12) whichprocesses the signal.

Signals representing data obtained by other means such as, for example,water content expressed as the water to oil ratio as measured by asuitable “add-on” instrument (74) (FIG. 4) integrated with the apparatus(10), may also be transmitted to the controller (12) for processing andanalysis.

The controller (12) may include any instrumentality or aggregate ofinstrumentalities operable to compute, classify, process, transmit,receive, retrieve, originate, switch, store, display, detect, record,handle, or utilize any form of information or data. For example, thecontroller (12) may be any suitable computer-system configuration,including hand-held devices, multiprocessor systems,microprocessor-based or programmable-consumer electronics,minicomputers, mainframe computers, and the like. Any number ofcomputer-systems and computer networks are acceptable for use with thepresent invention, provided they are installed in the hazardous areaclassification for which they are certified. The invention may bepracticed in distributed-computing environments where tasks areperformed by remote-processing devices that are linked through acommunications network. In a distributed-computing environment, programmodules may be located in both local and remote computer-storage mediaincluding memory storage devices. The present invention may beimplemented in connection with various hardware, software, or acombination thereof, in a computer system or other processing system.The controller (12) or computing unit may include a memory,computer-readable media comprising computer storage media, applicationprograms, a user interface, a video interface, and a processing unit.Although many other components of the controller (12) are not described,those skilled in the art will appreciate that such components and theirinterconnection are well known. The memory primarily stores theapplication programs or program modules containing computer-executableinstructions which are executed by the controller (12) for implementingthe described functions. The memory includes the data and statisticsprocessing module (14), the sensor feature map module (16), and the flowarea adjustment module (18). The controller (12) generates outputsignals to the positioner (52) and motor (54) based on feedback fromeach of the data and statistics processing module (14), the sensorfeature map module (16), and the flow area adjustment module (18).

Referring to FIGS. 2-4, exemplary methodologies of the present inventionwill now be described. At block 100, the multiphase fluid is directedfrom the transport line (not shown) into the entrance (22). Thetransducer (64) detects continuous real-time pressure oscillationscaused by density-transport velocity variations of the multiphase liquidflowing through the metering section (30), and transmits a correspondingsignal to the controller (12) for processing. Preferably, the signal iselectrical. A signal conditioner (102) eliminates or filters anyexternal noise and interference from the signal. The processed signal isthen transmitted to a data acquisition unit (104) which is controlled bya repeat/start module (106). When the controller (12) powers up (108),it generates a command through the OR block (110) to the repeat/startmodule (106) which activates the data acquisition unit (104). The dataacquisition unit (104) retains the processed signal for a predeterminedamount of time to collect a sufficient number of data points required toperform time-stable statistical analysis. As used herein, the term“time-stable” refers to the repeatability of characteristics extractedthrough conventional statistical data processing tools such as, forexample, the Probability Distribution Function (PDF). The data storageunit (112) subsequently receives a complete set of data representingtime-voltage signals collected over a specific period. Preferably, thetime-voltage signals are stored as 24 bit resolution signals.

The data processing unit (114) performs statistical analysis including,but not limited to, creation of sets of data points from the signals,development of probability density functions (PDF) from the sets of datapoints, and derivation of values for specific parameters from theprobability density functions. In one embodiment, the time-voltagesignals are divided into bands or holding bins (e.g., 1000 bins). Eachbin represents a different interval value for the amplitude of a voltagesignal group, and contains a number of voltage signals collected for thevoltage interval. These data are used to calculate the probabilitydensity function (PDF) which is defined as:f(x)=dF(x)/dx  Eq. (2)where:F(x)=Σx _(i) /n for i=0 to x and n=Σh _(j) for j=0 to 999 (i.e. 1000bins)  Eq. (3)

-   (j=number of bins) hj—elements of histogram representing the number    of times the acquired signal has a voltage value between    Vj−V(j+0.8)/number of bins

Statistical parameters that may be derived directly from the signals orfrom PDFs developed by processing the signals include, but are notlimited to, minimum signal value, maximum signal value, mean signalvalue, median signal value, variance, standard deviation of the PDF,skewness of the PDF, kurtosis of the PDF, and momentums of the PDF.Parameters that may be derived from other processing of the signalsinclude those related to the frequency of the signals, such as linearprediction model parameters and cepstrum function parameters, as well asthose which may be obtained from other mathematical processing of thesignals.

The preferred statistical parameters for determining the transportparameters are the maximum probability density function value(PDF_(max)) and the corresponding difference in the value of thePDF_(max) between two predetermined transport velocities obtained from apair of local reference movable flow diverter positions (“nearby” pairpositions). The PDF histogram has a specific kurtosis or histogram shapewhich is related to two-phase flow through the metering section (30).The PDF_(max) values are compared with the total processed number ofimpulses. Accumulation of all impulses in only a few bins (e.g., 1-5bins) centered by zero voltage value indicates that a single densityfluid is flowing through the metering flow area (30). A gas voidfraction ratio (GVF) about equal to 0 indicates only near liquid, whilea GVF about equal to 1 indicates only near gas. When discrete phaseelements are present (e.g., bubbles transported in a continuous liquidphase or droplets transported in a continuous gas or vapor phase),impulses of various voltages are obtained of a number strictly relatedto the number and size of all gas-liquid frontiers passing by themetering section (30). Extreme values of PDF_(max) may be indicative ofhigh transport velocities which lead to high turbulence and high-shearto yield a very fine structure of dispersed phase, behaving as a singlephase as the extremely small dispersed structures may not be able toenergize the acceleration sensor at all. All impulses are concentratedin a small number of bands (bins), and the PDF histogram shifts to acentral lower voltage zone, a condition also observed for gas or liquidflow only.

An expert unit (116) converts the movable flow diverter position “x”(58) and inputs from the PDF resulting from acceleration sensorprocessed impulses, from the pressure transducer (68), the differentialpressure transducer (66), the temperature transducer (72), and any otherinstrument (74) integrated with the apparatus (10) into engineeringunits, and evaluates the information from the data processing unit(114). The expert unit (116) is communicatively coupled to externaldevices such as, for example, a graphical user interface (118), tooutput and display observations and results to plant operatorscontinuously and in real time. Such observations and results mayinclude, but are not limited to, total transport velocity (U_(m)) andaverage thereof, the relative proportions of the gas and liquid phases(gas void fraction or GVF), daily accumulated volumes of liquid and gasfor a full month, monthly accumulated volumes of liquid and gas, and thelike (expressed for a certain gas and liquid analytical composition andat the meter pressure and temperature P,T, always reducible to thestandard condition usually indicated as P=101.325 kPa and T=15° C.).

The values for the specific parameters are validated by comparison witha set of sensor feature maps (120). The set of sensor feature maps (120)preferably comprises at least one map representing each signal as afunction of the property of the flowing multiphase fluid which is to bedetermined. In one embodiment, the method comprises the step ofcomparing each signal directly with the set of sensor feature maps (120)to determine the property of the flowing multiphase fluid. In oneembodiment, the method comprises the step of deriving a value for aparameter from each signal, and comparing the value of the parameterwith the set of sensor feature maps (120) to determine the property ofthe flowing multiphase fluid. Where the method includes the step ofderiving parameters from the signals, the set of sensor feature maps(120) preferably comprises at least one map for each parameter as afunction of the property of the flowing multiphase fluid which is to bedetermined. The set of sensor feature maps (120) may also comprise a setof graphs in which the property is expressed either as a function of thesignal or of a parameter derived from the signal (FIGS. 7, 8A-B).

Based upon a comparison with the set of sensor feature maps (120) whichpreferably includes the PDF and a normalized gas-liquid flowcharacteristic such as, for example, normalized transport velocityU_(m), wherein if the characteristics are expressed analytically such asPDF=F(U_(m))_(@GVFi), a corresponding set of derivatives is obtainablethrough conventional mathematical methods such as, for example:[d(PDF)/d(Um)]@GVFi=F(Um,GVF)  Eq. (4)The expert unit (116) decides whether the fluid may include only a gasphase or only a liquid phase (122), or both (124). If the fluid includesonly a gas phase or only a liquid phase (122), the expert unit (116)calculates the single phase flowrate using known equations of state(i.e., PVT methods known to those skilled in the art), and transferssubsequent metering tasks including the pressure drop (66) (FIG. 3) to aconventional, single-phase integrated metering algorithm (126). In thealternative, if the fluid includes both gas and liquid phases (124), theexpert unit (116) proceeds to determine transport velocity (U_(m)), andgas concentration expressed as gas void fraction [GVF (−)] in m³/m³(128) using the gas and liquid flowrates (Q_(G), Q_(L) in m³/h) (130).

The transport velocity (U_(m)) at a certain flow section indicated asA_(flow) is defined as:U _(m)=(Q _(G) +Q _(L))/A _(flow)  Eq. (5)wherein A_(flow) is the metering flow area for a certain apparatusdesign and for a known position of the movable flow diverter (MFD) (x).The gas void fraction is defined (for the homogenized gas-liquidpre-conditioned in the flow area only) as:GVF=Q _(G)/(Q _(G) +Q _(L))  Eq. (6)Once GVF and Um are determined, the expert unit (116) can calculate thegas and liquid flowrates as follows:Q _(G)=GVF·Um*A _(flow)  Eq. (7a)Q _(L)=(1−GVF)·Um·A _(flow)  Eq. (7b)where Um has the velocity units (m/s) as converted for the dimensionlessvalue customarily used in the sensor feature maps or reference operationcharacteristics (ROC).

In one embodiment, the transport velocity and gas void fraction arestored in the database using cubic function interpolation or direct datatable search, and retrieved using a search-match process as furtherdescribed. Based on results from these calculations, the expert unit(116) queries whether or not the measurement of the fluid lies in alinear, accurate, and stabilized metering condition (132). This isconfirmed by obtaining a set of measurements for a pair of “nearby” orlocal positions (134) for same movable flow diverter positioncomparative assessment. The pair positions (x1, x2) are identified to beproximate the initial or “home” measuring position (xi) such that thehome measuring position (xi) becomes median between the pair positions(x1, x2). In one embodiment, the movable flow diverter positions (x1,x2) are proximate the home measuring position (x₁₋₂) by relatively smalldisplacement distances of the movable flow diverter (48). In oneembodiment, the median position xi1-2 is identical to x1.

A command is initiated through the OR block (136) to output a signal tothe positioner (52) to relocate the movable flow diverter (48) to thetarget position (x1, x2). A feedback signal (58, 56 g; FIG. 3) from theflow area adjustment module (18) is monitored and assessed to determinewhether the movable flow diverter (48) has reached the target position(x1, x2) within a predetermined time delay (138). At block (140) it isdetermined whether or not the movable flow diverter (48) is in thetarget position (x1, x2) to acquire a set of measurements. If themovable flow diverter (48) has not reached its target position (x1, x2)within the allotted time, an alarm (142) triggers to alert plantoperators. In the alternative, if the movable flow diverter (48) hasreached the target position, the repeat/start (106), enabled through OR(110), instructs the data acquisition unit (104) to start recordingsignals from the monitoring devices (58, 66, 68, 72, 74).

Once set to the first local position (x1), the movable flow diverter(48) remains stationary for a sufficient amount of time to allow a firstset of data to be collected from the monitoring devices (58, 66, 68, 72,74). After the first set of data has been collected, the movable flowdiverter (48) is set to the second local position (x2) at which itremains stationary for a sufficient amount of time to allow a second setof data to be collected from the monitoring devices (58, 66, 68, 72,74). Successively repositioning the movable flow diverter (48)back-and-forth between the first and second local positions (x1, x2)allows collection of additional sets of data to recalculate and refreshthe liquid and gas flowrates values periodically.

The total amount of time for metering (i.e., repositioning the movableflow diverter (48) to each of the first and second local positions (x1,x2) and for collecting a set of data at each of the first and secondlocal positions (x1, x2)) may be relatively brief. In one embodiment,the total amount of time for metering ranges from about 10 seconds to amaximum of about 60 seconds. This speed of metering may be attributed tosmall changes in movable flow diverter position using the localpositions (x1, x2) and the short data collection time. Regardless ofsuch brevity, metering in this manner generates measurable parametersand sufficient data. Although when the metering section (30) (hence, thegas-liquid transport velocity) is only slightly altered, the compositionof the multiphase fluid at the entrance (22) and the inlet gas-liquidtotal flowrate are negligibly changed, indicating the insignificanteffect the movable flow diverter (48) repositioning to a “nearby”metering position x1-x2 has on the apparatus recovery pressure (FIG. 6,Example 2).

The collected data from the monitoring devices (58, 66, 68, 72, 74) aretransmitted, processed, analyzed, and validated in the same manner asdescribed above. Once a set of parameters (i.e., transport velocityU_(m) found as median between two “nearby” metering positions x1-x2 orat one extreme as x1 or x2) for the local pair positions (x1, x2) hasbeen calculated and compared to the parameters obtained from the homemeasuring position (xi), the expert unit (116) decides whether themeasurements are acceptable or unacceptable, and initiates appropriateaction. The sensor feature maps (120) indicate the expected transducerresponse to similar gas-liquid transport velocity, GVF, and gas-liquiddensity difference, provided that the multiphase fluid is properlyconditioned for the metering section (30) within the apparatus (10) andlocally, inside mainly the metering section (30), and practicallybehaves as a homogenous gas-liquid mixture. If at block 132, it isdetermined that the measurements are acceptable, metering is maintainedin the suitable metering section (30) (i.e., home measuring position(xi) defining the pair x1 and x2) as long as the external system flowconditions (as input) do not noticeably change. Measurements areconsidered acceptable when it is determined they take place in a linear,accurate and stabilized metering condition, where “linear” indicates aproportionality between pairs of movable flow diverter positions xi andflow area and subsequently, gas-liquid transport velocities U_(m1),U_(m2).

In the alternative, if at block 132, it is determined that themeasurements are unacceptable, a “search” is triggered for bettermetering flow conditions (144) by seeking a new movable flow diverterposition (i) and the condition is assessed for a second pair of localpositions (x3, x4). Determination of acceptable measurements is againconfirmed by first assessing the “quality” of the metered parameter andthen using the set of sensor feature maps (120) for gaining furtherinformation. As shown in the sensor feature map of FIGS. 8A-B forexample, the density of the PDF contour lines significantly increases atboth very low and extremely high GVF, at which the PDF approaches amaximum value and decreases towards a central zone plateau. High densityPDF contour lines may indicate extreme gas, low liquid conditions (highGVF); extreme liquid, low gas conditions (very low GVF); and/or extremehigh gas and liquid flow rates leading to a fine, homogeneous gas-liquidflow where the dispersed phase is too fine and transport velocity is toohigh for transducer and system sensitivity (i.e., for measuringtime-acceleration pressure-voltage). Unacceptable measurements thusinclude, but are not limited to, those relating to an excessively highGVF indicating only a gas phase (e.g., GVF>0.95); an excessively low GVFindicating only a liquid phase (e.g., GVF<0.05); a “noisy” PDFindicating variable input flow-pressure conditions caused by eithersignificant flowrate and/or composition variation or major input flowchange or extremely low transport velocities or stagnant conditions; andthe like. Unacceptable measurements indicate a need to re-adjust andrestore suitable metering conditions by “moving out” from high-densityzones as indicated by the sensor feature maps.

To conduct a “search” for better metering flow conditions, the meteringsection (30) is significantly changed by displacing the movable flowdiverter (48) to a “new” home measuring position (new xi). In oneembodiment, the movable flow diverter (48) is sizably displaced three toten times the distance customarily considered as x1-x2 (nearby distance)(depending on the specific configuration of the movable flow diverter(48) and housing (32)). In the manner described above, a set ofmeasurements for new pairs of “nearby” or third and fourth local homepositions xi(i=3,4) is initiated and obtained. The third and fourthlocal positions (x3, x4) are identified to be proximate the “new” homemeasuring position (new xi) such that the new home measuring position(new xi) becomes median between the third and fourth local positions(x3, x4).

Once set to the third local position (i=3), the movable flow diverter(48) remains stationary for a sufficient amount of time to allow a setof data to be collected from the monitoring devices (58, 66, 68, 72,74). After the set of data has been collected, the movable flow diverter(48) is set to the fourth local position (i=4) at which it remainsstationary for a sufficient amount of time to allow a second set of datato be collected from the monitoring devices (58, 66, 68, 72, 74).Successively repositioning the movable flow diverter (48) back-and-forthbetween the third and fourth local positions (i=3, 4) allows collectionof additional sets of data. The data are transmitted, processed,analyzed, and validated in the same manner as described above, includingdetermination of acceptable or unacceptable measurements at block (132)and initiation of subsequent action at block (134) or block (144).

Through repeated measurements, the expert unit (116) eventually locatesthe suitable metering section (30) by changing the position of themovable flow diverter (48) and implicitly the flow metering area atwhich measurements are taken, and continuously collects measurements atthe suitable metering section (30), provided that the external flowconditions do not significantly change. In this manner, the expert unit(116) becomes trained over time and learns specific critical flowconditions encountered such that in the event of a change, remedialaction can be taken to maintain a linear, accurate, and stabilizedmetering condition. In the event that the flow conditions change and themeasurements may indicate an unstable metering condition, the meteringsection (30) is subsequently altered by displacing the movable flowdiverter (48) until the measurements being collected indicaterestoration to a linear, accurate, and stabilized metering condition.

The foregoing apparatus, system, and method described herein areparticularly useful in continuous, real-time monitoring of a single wellor multiple wells simultaneously, with each well equipped with its ownapparatus. The apparatus is able to display the flowrate and gas-liquidratios (e.g., oil, water, gas) for each well in the field prior toreaching or bypassing a tank separator. The invention may enableproduction optimization for an entire field to increase overallproduction and to implement effective reserve savings procedures.

Although various embodiments and methodologies have been shown anddescribed, the invention is not limited to such embodiments andmethodologies and will be understood to include all modifications andvariations as would be apparent to one skilled in the art. It should beunderstood that the invention is not intended to be limited to theparticular forms disclosed. Rather, the intention is to cover allmodifications, equivalents and alternatives falling within the scope ofthe invention as defined by the appended claims.

Embodiments of the present invention are described in the followingExamples, which are set forth to aid in the understanding of theinvention, and should not be construed to limit in any way the scope ofthe invention as defined in the claims which follow thereafter.

Two groups of numerical examples and calculations are presented:

In Examples 1 and 2, the pressure drop across the flow diverter packageis evaluated using a 2″ apparatus design and given flowrate andgas-liquid ratio.

Calculations performed for estimating the non-recovered pressure dropfor a certain flow diverter position (x) and for a range of movable flowdiverter positions, are essential for assessing the potential impact ofthe movable flow diverter and housing configuration to systempressure-flowrate characteristics. A significant differential pressureduring a small movable flow diverter displacement may negatively impacton the “constant flowrates assumption” for the apparatus operationdesign.

The “homogeneous two-phase flow” assumption was used to calculategas-liquid inlet properties. A double cone flow model (Crane model) hasbeen used to simulate and simplify the complex modifications of flowarea across the movable flow diverter and housing (also indicated as“stationary flow diverter” (FIGS. 5, 6A). The non-recovery pressure dropresults calculated for a range (as 80 to 110 mm for the used design) ofmovable flow diverter positions (xi) and implicitly the position andvalue of minimum flow area at the conjunctions of the two-cone flowmodel (FIGS. 6A, 6B), using the Crane model (initially validated forone-phase flow only) are further compared with the results using the“Owen-Wade” model (validated under two-phase flow conditions).

Calculated non-recovered differential pressure drop (for data used inthe example; Tables 1-3) and for movable flow diverter displacementsranging from 50-110 mm (FIG. 6B, right) and gas-liquid flowrate data (asin the medallion FIG. 6B, right) is in the range of 0.01-0.04 psi(0.07-0.28 kPa). The relatively low range of non-recovered pressureconfirms that the effect of pressure change during a pair meteringoperation (small displacement of MFD) is very small and could beignored; therefore, the constant fluid inlet condition during a pairmetering procedure is considered to be practically valid, and is furthersupported by assessing the potential errors due to pressure-flowratesystem alterations (Example 2).

In Example 3, information obtained from the sensor feature maps databaseand the nearby PDF pair measurement are combined with the modificationof the metering section to evaluate the transport velocity (Um) and thegas void fraction (GVF). The pair flow diverter positions are simulatedusing actual apparatus design data. The “solution searching” operationprocedure is introduced by combining key information extracted from thesensor reference maps and area flow changes during movable flow diverterdisplacement for acquiring a pair of metered PDF values in order todetermine the appropriate Um and GVF values.

Example 1

The movable flow diverter and housing are configured to prepare theincoming (vertical) gas and liquid inflow to enter the metering sectionand properly guide the metered mixed fluids to re-enter the system pipeflow. Small variations of metered transport velocity and relatedmetering section are induced through precisely controlled movable flowdiverter displacement (x). Small displacement of the movable flowdiverter and related modifications of transport velocity due to precise,known modification of the metered flow area (Ak) induce measurabledifferences of PDF causing neither noticeable change of the incoming gasand liquid flowrate nor modifications of the gas-liquid ratio (as GVF).The introduction of only minor system pressure-flowrate variations andminor changes of gas-liquid equilibrium without impacting the meteringaccuracy makes this possible.

Referring to FIG. 6A (and using FIG. 5 as base—both using the mobileflow diverter position xi=80 mm as an example) as the actual apparatusand the model adopted for recovery pressure drop, the specific designallows for a correlation indicating the length of the “compression” zone(as “1” in FIG. 6A, right) and the “expansion” zone (as “2” in FIG. 6A,right) as a function of the movable flow diverter position “xi” (seeFIG. 5 as xi=80 mm):Lc(compression)=200−L(expansion)  Eq. (8)Le(expansion)=xi+14  Eq. (9)Additional information for the calculation included the following:

1. (A_(min)/A_(o))=0.4 (for x_(iflow diverter)=80 mmonly)—Computer-generated for the particular design for 50<xi<80 mm ascalculation prerequisite using the detailed design features.

2. Dmin/Do=(Amin/Ao)^(0.5)=0.63

3. Do=49.5 mm (1.95 inches)—design 2″ apparatus/loop

4. Lc≈x(movable flow diverter)+14 mm−(Lc=80+14=94 mm)

5. Le=200 mm−Lc (mm)−(Le=200-94=106 mm)

Equations 10-12 are used to calculate the non-recovered pressure drop ina double-cone flow model as ΔP expressed in Pa (eq. 11). The pressuredrop in an area change, short flow element, is customarily calculatedknowing the inlet gas-liquid densities (a homogeneous gas-liquid density(ρ_(mo), kg/m³) is calculated as a function of the gas and the liquiddensities and the GVF), and the square of gas-liquid inlet transportvelocity (U_(mo), m/s). For specific units in eqs. 10 and 12, theacceleration due to gravity (g≡9.81 m/s²) is used:

$\begin{matrix}{{h(m)} = {K_{1,2}\frac{U_{mo}^{2}}{2\mspace{11mu} g}}} & (10) \\{{\Delta\;{P({Pa})}} = {{K_{1,2} \cdot \rho_{mo}}\frac{U_{mo}^{2}}{2}}} & (11) \\{{\Delta\;{P({Pa})}} = {\rho_{mo} \cdot g \cdot {h(m)}}} & (12)\end{matrix}$

Equations 10-12 introduce two empirical (experimental) constants K_(1,2)depending on the specific design as further introduced through eqs.13-16 and calculated for particular flow diverter positions (e.g., x=30,50 and 80 mm; Table 1).

For cone angle (θ<45° as velocity profile in the apparatus; FIG. 6A,right) empirical constants K_(1,2) are expressed as:

$\begin{matrix}{K_{({contraction})} = {\frac{0.8 \cdot ( {1 - \beta^{2}} )}{\beta^{4}} \cdot {\sin( \frac{\theta}{2} )}}} & {{Eq}.\;(13)} \\{K_{({expansion})} = {\frac{2.6 \cdot ( {1 - \beta^{2}} )^{2}}{\beta^{4}} \cdot {\sin( \frac{\theta}{2} )}}} & {{Eq}.\;(14)}\end{matrix}$where the recovery pressure drop value (FIG. 6) is obtained in Pa (or ash_(mH2O) equivalent); where the cone angles (β_(1,2); FIG. 5) areseparately obtained for the entrance and exit cones as:

$\begin{matrix}{\beta = \frac{D_{\min}}{D_{({{in}\text{/}{ex}})}}} & {{Eq}.\;(15)} \\{( \frac{\theta}{2} ) = {{arc} \cdot {\tan\lbrack \frac{( {D_{{in}/{ex}} - D_{\min}} )\text{/}2}{L_{{{({cone})}1},2}} \rbrack}}} & {{Eq}.\;(16)}\end{matrix}$

TABLE 1 Gas-liquid pressure, flowrates and quality (x) - inletstationary flow diverter (MFD Stem as Case #3) P_(entr) Qg Ql Um GVF xkPa m³/h m³/h m/s (—) (—) 118.69 2.59 4.00 0.81 0.39 1.19E−03

Table 1 (also FIG. 6B, medallion) summarizes the fluid inlet pressureand flowrates for gas (air) and liquid (water) at the apparatus inletmeasured conditions (pressure and temperature). The gas-liquid “quality”(x) has been introduced as it is used by the Wade-Owen model and isdefined as: x=Gg/(Gg+Gl) as kg/kg, where G indicates the gravimetricflowrate (g—gas, l—liquid). It can be directly related to GVF for knowngas-liquid densities and for homogeneous flow only.

Table 2 summarizes geometrical key elements calculated as a double-conesimulating the flow area profile (for example, xi=80 mm; FIG. 5, right;FIG. 6A, left) in the apparatus for movable flow diverter positions xias x1=30, x2=50 and x3=80 mm (data calculated for the specific flowdiagram according to equations 8, 10, and 13-16). The movable flowdiverter position (xi) and shape, together with the specific design ofstationary flow diverter, impact on positions and size of minimum flowarea—a key value considered for the two-cone model used for pressuredrop calculation (FIG. 6B).

TABLE 2 Relevant Geometry Model Data (for three positions of movableflow diverter - MFD) Ao Do Ao Do Ao Do MFD Position m² mm MFD Positionm² mm MFD Position m² mm xi 0.00193 49.53 xi 0.00193 49.53 xi 0.0019349.53 mm Amin (m²) A/A min mm Amin (m²) A/A min mm Amin (m²) A/A min 300.00117  0.61 50 0.00111  0.58 80 0.00098  0.51 Ac/Ao (—) Dmin/Do (—)Dmin (mm) Ac/Ao (—) Dmin/Do (—) Dmin (mm) Ac/Ao (—) Dmin/Do (—) Dmin(mm) 0.61 0.778 38.54 0.58 0.760 37.65 0.51 0.714 35.39 1. Lc (mm) 2. Le(mm) 1. Lc (mm) 2. Le (mm) 1. Lc (mm) 2. Le (mm) 44 156.00 64 136.00 94106.00 β β β β β β 0.778 0.778 0.760 0.760 0.714 0.714 θ/2 (rad) θ/2(rad) θ/2 (rad) θ/2 (rad) θ/2 (rad) θ/2 (rad) 0.12 0.04 0.09 0.04 0.080.07 deg deg deg deg deg deg 7.12 2.02 5.30 2.50 4.30 3.82 K (contr) K(exp) K (contr) K (exp) K (contr) K (exp) 0.11 0.10 0.09 0.14 0.11 0.33

Results of calculations indicating the non-recovered pressure drop atdifferent flow diverter positions as (50<xi<80 mm) are illustrated inFIG. 6B. Gas and liquid flowrates at the flow diverter inlet are shownin FIG. 6B (medallion) and, for three fixed positions of movable flowdiverter (MFD) as x(i)=30, 50 and 80 mm in Table 2. In addition to“Crane” Double Cone Model (adapted for actual gas-liquid flow), thenon-recovered differential pressure across the movable flow diverter andhousing was calculated according to Wade (1989, Int. J. Multiphase Flow15, pp. 241-256) and Owen (1992, Int. J. Multiphase Flow 18, pp.531-540).

FIG. 6B (right) illustrates the calculated results for non-recoveredpressure loss (eq. 11) using a simplified double cone simulated flowarea model (FIG. 6B, left), where constants K1,2 (eqs. 13-16; Table 2)are evaluated for each movable flow diverter position (x=50-110 mm—Table2—extract for x1=30,50 and 80 mm). Results using the adopted Crane modelare compared to the Owen-Wade Model (as O-W FIG. 6B, right) (validatedfor gas-liquid flows) for the same input flow data and simplified flowdiverter design (Design #3; Table 1; FIG. 6B, right; Medallion).

For the gas-liquid flowrates considered (as approximately 134.4 CMD or845 equivalent gas and liquid BBD in a 2″ line), the range of calculatednon-recovered pressure drop is approximately 0.07-0.28 kPa (0.01-0.04psi), suggesting a relatively small value for any industrialflow-pressure common flow system. Results from the two models areidentical only for the flow diverter position (xi=98 mm); however, theyare within the same order of magnitude. The results suggest that theapparatus of the present invention is distinct from any control valve,and that the streamlined flow as a result of particular configuration ofthe flow diverter and housing substantially eliminates the risk of gasexholution and flow detachment observed during the use of conventional(one-phase) metering equipment for metering the two-phase petroleum flowproducts. However small, the pressure modifications during minutiae flowdiverter displacement may induce errors related to modifications ofinlet flowrate, and this was further investigated.

Example 2

A pair metering operation (small displacement of movable flow diverter)was simulated to assess the small displacement effects of movable flowdiverter on inducing non-recovery system-pressure variations, and to usethe calculated non-recovery pressure variations to assess the potentialalterations of flowrates due to modifications of the pressure-flowrate“feeding” the system. The geometry of the apparatus described in Example1 was used. The “home” position was 80 mm (FIGS. 5, 6) and the pairposition was 81 mm (1 mm displacement—The “Design #3” of flow divertersystem was adopted—see FIG. 6B (right) calculated non-recovered pressuredrop). Table 3 summarizes the modifications of non-recovered pressuredrop calculated using the Crane model (Table 3—“Model 1”) and theOwen-Wade model (Table 3—“Model 2”), the metering flow area (Ak/Ao), andthe respective transport velocity in the metered area (Ak). The inputflowrates from Table 2 were used.

TABLE 3 Non-recovered pressure drop, metering area and transportvelocity Position DP Model 1 DP Model 2 Metering Area Ratio andTransport Velocity MFD Tot DP Δ (DP1) Tot DP Δ (DP2) Ak/Ao Um (k) D_lessΔ (Um) mm kPa Pa = kPa × 1000 kPa Pa = kPa × 1000 (—) m/s (—) (—) 800.0908 0.1508 0.542 1.4909 0.3516 81 0.0934 2.5993 0.1514 0.5904 0.5391.4975 0.3532 0.0015

Table 3 indicates a modification of non-recovered pressure drop ofapproximately 0.6 Pa; however small, this may be a potential source ofapparatus metering error. To estimate the magnitude of potential inletflowrate modifications, a centrifugal, industrial (25 HP) liquid pumpwas assumed to feed the apparatus with liquid.

The effects of small displacements of movable flow diverter (MFD) upon acertain pressure-flowrate system profile were evaluated. The “system”pressure-flowrate profile is found in many engineering applications suchas the “pump head versus flowrate characteristic or the reservoir inflowproduction relationship (or IPR). A baseline inlet liquid flowrate of 4m³/h was assumed.

The external flow system was introduced through the head-pressurecharacteristic of an industrial pump. The modifications of pressure dropintroduced in the flow system by the apparatus were further used toassess the potential induced changes of system delivered liquid. Eq. 17is a fair analytical model of head (m H₂O) versus pump flowrate Q(m³/h)—as for the arbitrarily selected 25 HP pump:P(head as m H2O)=˜0.0032·Q ²+0.1384·Q+58.715  Eq. (17)

Eq. 17 simulates the system pressure-flowrate characteristic. Using eq.17, at a pump head of 59.22 m H₂O, the pump discharge would beapproximately 4 m³/h. Eq. 17 is further linearized for a smallhead-flowrate range of interest to obtain (by also inverting variables)an equation describing the flowrate Q as a function of head (or flowresistance in the system) as:y(m³/h)=a+bx (Head mH₂O)  Eq. (18)

-   -   where the coefficients a=−521.7007 and b=8.8775

The linearization coefficients a, b, are be valid for a range of4>Q>4.02 m³/h (only). Eq. 18 (as for operation range detail) is furtherused to assess the potential modifications induced by the change ofnon-recovery pressure of 0.590 Pa (Table 3), change related to movableflow diverter displacement (from 80 to 81 mm). The calculateddifferential non-recovery pressure (as in Pa Table 3) is converted toH(mH₂O) as:DP(80-81 mm):0.590441 Pa=5.90441×10⁻⁵(mH₂O)  Eq. (19)

Using Eq. 18, results indicating expected flowrate modifications duringmovable flow diverter displacement (80 to 81 mm) are summarized in Table4:

TABLE 4 Potential errors due to pressure-flowrate “system” alterationsduring the movable flow diverter advancement from a “home” to a “nearby”metering pair position Pressure Liquid Rate mH₂O m³/h Base Line MFD 80mm 59.2174000 3.9999963 New MFD MFD 81 mm 59.2174590 4.0005205 SystemFlowrate Modifications L/min Base Line Baseline 66.667 DQ System 0.009Meter Error % err. 0.0131The results indicate a potential metering error in the range of 0.013%or 0.009 L/min compared to baseline (4 m³/h or 66.67 L/min). This isconsidered acceptable for the apparatus operating in an actual liquidfeeding pressure-flowrate field installation system.

Previously presented simulated apparatus operation conditions werefurther used to assess the modifications of PDF values during theimplementation of a pair-metering task. The inlet flow data from Example2 and Table 2 were used. However, this simulation was used to introduceand apply the sensor feature maps and database. The sensor feature mapswere obtained using an acceleration sensor of known response propertythat was exposed to numerous gas-liquid flows of various GVF and broadranges of gas-liquid transport velocities. During experimentalsensor-fluids testing (data not shown), it was found that therepeatability of extracted PDF for the same fluid pair at the sametransport velocity (Um) and gas void fraction (GVF) is almost perfect(less than 0.1% error). Data collected were subsequently organized usinga three-dimensional (PDF-Um-GVF) data display and used as a base for thesensor reference operation characteristics (ROC) as further introducedby FIGS. 8A-B.

FIG. 7 shows an extracted sensor feature map (also as referenceoperation characteristic—ROC for constant GVF=0.4 as PDF=F(Um). The GVFwas selected to coincide with the input data used for calculating therecovery pressure (Table 2). A U-shaped feature of unique, identifiableposition in the PDF-Um map coordinates is a characteristic observed forbroad ranges of dimensionless transport velocities (Um). This functionis accurately modeled using a cubic fit polynomial equation (FIG. 7,Medallion), analytical formats further used in one embodiment ofcalculation procedures. The minimum value as PDF≈0.7 suggests that formetered PDFS (as PDF<0.7), there would not be any potential Um solutionand the metered section should be reduced by modifying the movable flowdiverter position. At the minimum value (as dimensionless velocitiesUm=0.33), the signal obtained from the acceleration sensor placed in themetered area (as A-A in FIG. 5, left) is most evenly distributed in bins(1000 bins considered as standard for this application). At both higherand lower Um values (only for GVF=0.4), the PDF is higher, indicating anincrease of signals collected in the “central bins” (of smallervoltages). At very low dimensionless velocities Um, the PDF approachesPDF=1−a clear sign of approaching the “one fluid-one density only”flowing system and acceleration sensor limitation. At very high valuesof Um (not observed in FIG. 7 due to sensor flow testing limitations),the PDF approaches again a maximum value close to 1, an effect due tothe formation of extremely fine dispersions of gas-liquid systems, thatwill practically not energize the particular acceleration sensor, andbehave as “one phase.”

Information from the sensor feature map for PDF=0.4 (FIG. 7) wascompared to dimensionless transport velocities (input flow data fromTable 2) and PDF's were obtained for the specific configuration ofmovable flow diverter and housing (or stationary flow diverter) as setout in Table 5.

TABLE 5 The expected PDF variation during movable flow diverter (MFD)displacement Position Um GVF = 0.4 MFD D_less x(MFD) Um PDF mm (—) mm(—) (—) 80 0.35163 80 0.3516345 0.71542 81 0.35317 81 0.3531746 0.71563Diff (%) 0.436 0.028

Table 5 indicates the PDF as calculated from the cubic equation (forgiven Um values) obtained from ROC for PDF=0.4 (equations in FIG. 7,medallion). The sensor reference operation characteristic (ROC) may befurther used to determine (from the indicated cubic equationPDF=F(Um)GVF=0.4) the value of PDF expected for the dimensionlessvelocities pair. Table 5 also indicates the percentage PDF modificationsduring the movable flow diverter displacement, suggesting that theaccuracy required during the metering operations of the PDFs, must be,particularly high. Um and GVF (implicitly Q_(L) and Q_(G)) are unknownquantities, with the only available information being the PDF's at apair of “nearby” metering locations of known displacement values and ofknown metered area values (simply related to movable flow diverterposition and specific apparatus design). The actual metering problemresides in how to use the two PDF metered values, the sensor featuremaps, and the flow area modifications for the pair movable flow diverterpositions to find the Um and GVF. Example 3 addresses this issue, wherethe present invention is used to find the transport velocity (Um) andthe gas-liquid proportion (GVF) when the PDF is obtained for two“nearby” positions (PDF1, PDF2).

Example 3

A metering case was conducted using a simplified procedure.Demonstrating this procedure requires a valid PDF1, PDF2 pair. Theobjective was first to generate a measurement pair PDF1 and PDF2 toensure it was a valid pair and then outline a method of finding Um andGVF from this pair as if it were a measurement pair obtained through anactual measurement. The following information is known:

a. Gas void fraction: GVF = QG/Qm = 0.4 (—) b. Gas-liquid transportedflowrate Qm = QG + QL = 2.65 (m3/h) c. Home position of movable flow x1= 85 mm diverter (MFD): d. The “Nearby” MFD position: x2 = 86 mm e.Metering flow areas at positions Ak1/Ao = 0.529, x1 and x2: Ak2/Ao =0.527 (—) (a relative value of flow area - calculated using the knownentrance area Ao = 0.0019 m² of a 2” pipe and the geometry of themovable and stationary flow diverters).

Under the reality of the apparatus metering procedure using datacollected from the acceleration sensor with the MFD at position x1 andx2, two salient pieces of information indicated as PDF1 and PDF2 arefurther calculated as per Eqs. (2) and (3). These will be referred to asmeasured PDFs.

For this calculation example, in the absence of a tested case, it isassumed first that GVF and the transported gas-liquid flowrate Qm areknown quantities, and with known values of pair metering position x1,x2,the values of PDF1,2 (as “seed”) are calculated using the sensor mapequations. The example will show a methodology of how to find GVF and Umwhen PDF1,2 are known, using these calculated PDF values. Table 6summarizes input data. Data introduced at rows #3-#5 are normallyavailable during any metering procedure including a pair of valuesobtained from the “home” position of movable flow diverter (MFD) atx1=85 mm and the “nearby” MFD position at x2=86 mm (selectedarbitrarily).

TABLE 6 Summary of input data for “GLIMS #3” Apparatus Model (Example#3) # MFD Pos. 1 MFD Pos. 2 1 Qm = Q_(G) + Q_(L) (m³/h) 2.78 2.78 2 GVF(—) 0.4 0.4 PAIR METERING Home Nearby MFD—Mobile Flow Diverter Positionmm mm 3 85 86 4 Metering Area Ak/Ao (“GLIMS#3”) 0.52909 0.52664Gas-Liquid metering area velocity Um Um1 Um2 Note: for Ao = 0.001927 m²m/s m/s 5 (2″-GLIMS #3) 0.7564 0.7599 Um1 Um2 Normalized meter. areavelocity (—) (—) 6 0.1719 0.1727 PDF PDF1 PDF2 7.0 PDF [as F(GVF = 0.4)from “ROC”] 0.79999 0.79923 7.1 PDF [for GVF = 0.4 as FIG. 7 0.800130.79937 Medallon]

Actual and normalized velocities (for the pair MFD positions) can beobtained from the known Qm and the profile of the metered flow areaAk=F(xi) (FIG. 5 “Metered Flow Area” A-A). For the specific design ofmovable and stationary flow diverter indicated in Table 6 as “GLIMS #3”,Ak=F(x1) is thus precisely known for 40<xi<150 mm, where xi is the MFDposition in mm. For the pair metering positions, Table 6 indicates thetwo metered areas in row #4. The anticipated data of transported flowrate (row #1) Qm=2.78 m³/h (for the actual pressure-temperature measuredfor the metered area Ak) is used to determine the actual transportvelocities in the metered area Ak and from the actual the normalizedtransport velocities by using Um max=4.4 m/s (rows #5 and #6; Table 6).

To calculate the PDF1,2 (row #7; Table 6), the corresponding functionPDF=F(Um) for GVF=0.4 (as assumed first, Table 6, row #2) is extractedfrom the existing “Sensor Feature Map” database (Module #16, FIG. 2).FIG. 7 shows the graph of this extracted function, the cubic equationpresented in the medallion being its analytical form. The coefficientsof cubic equations in the actual database contain more decimals thanshown in the medallion of FIG. 7. Such precise coefficients were used todetermine the two PDF values shown in row #7 (Table 6).

FIG. 9, used as a template for Example 3, shows “seeded” PDF1,2 valuesas constant, horizontal lines in the graph depicting PDF versus a broadarbitrary Um range. Although two PDF values are extremely close, themagnified scale is shown for clarity; however, the PDF, determinedthrough apparatus pair measurements procedures, is a numericalstatistical representation of a distribution involving approximately 5million impulses. The precision is obtainable through data processing,is unrelated to physical units, and can be calculated with a highprecision decimal point.

Now that a valid PDF1 and PDF2 pair has been established, the a-prioriknowledge of GVF and Qm (Table 6 rows #1,2) values used to analyticallydetermine PDF1,2, can be ignored and one can proceed outlining a methodof finding GVF and Um when PDF1 and PDF2 are known measured quantities.The reality of the measurement procedure, at given fluid pressures andfluid temperature, as well as composition of gas and liquid (asdetermined in the field, with the aid of high-temperature gaschromatography), PDF1,2 and flow areas Ak1,2 at which the two PDF wereacquired are precisely known. In addition, the metered procedure makesuse of the sensor data base module (#16, FIG. 2) represented forexample, by a large group of sensor response cubic equations indicatedas PDF=F(Um)_((GVF)).

This example illustrates one approach for finding the actual GVF and Qm.In order to exemplify numerically the approach used for Qm, GVFdeterminations, three sensor feature map cubic equations (for GVF=0.2,0.4 and 0.8) are used and extracted from Module #16 (FIG. 2).

Using the same Um-PDF co-ordinates as FIG. 9, FIG. 10A is a graphicrepresentation of the three extracted cubic sensor characteristics. Forbrevity, the PDF=F(Um) for GVF=0.4 coincides with the conditionsinitially introduced in this example. Even for an extremely reducednumber of sensor feature maps, five potential (normalized) transportvelocities would be possible (in the range of approximately Um1=0.15 toUm5=0.5). For some “U-Shaped” sensor maps (such as for PDF=0.2 and 0.4)and for the specific PDF1,2 range, there may be two potential solutions.

Through known algebraic operations, knowing the coefficients (C00 . . .C03) of (selected GVF) cubic equations (Module #16, Sensor Feature Map,FIG. 2], and the PDF1,2 values (Table 6, row #7), the analyticalsolutions (as Um1,2,3) of the cubic equations are determined by solvingEq. 20:PDF(GVF)=C00+C01·Um+C02·Um ² +C03·Um ³  Eq. (20)

Table 7 is a summary of all potential Um solutions of the threeanalytical equations used for this example (see also Medallion, FIG. 10Awhere x≡Um).

TABLE 7 Summary of cubic equations solutions representing potentialtransport velocities MFD (x) #1, #2 PDF GCF Um11 Um21 Um31 x1 PDF1 =0.79998 0.2 0.164298 −0.39747 0.267519 x1 PDF1 = 0.79998 0.4 0.171911−0.70889 0.476807 x1 PDF1 = 0.79998 0.8 0.309823 img Cmx img Cmz PDF GVFUm12 Um22 Um32 x2 PDF2 = 0.79922 0.2 0.165426 −0.39765 0.266566 x2 PDF2= 0.79922 0.4 0.172710 −0.70909 0.476213 x2 PDF2 = 0.79922 0.8 0.311601img Cmx img Cmz

As observed in FIG. 10A, each extracted sensor feature map(GVF—specific) curve is distinct as it occupies a different space in thePDF=F(Um) display; intersects the “known” PDF1,2 at a different value ofUm (indicated for the example in FIG. 10A as Um1 . . . 5; and eachsensor feature curve intersects the PDF1,2 zone indicating a different,yet, apparently unique slope value as ΔPDF1,2/ΔUm1,2 (FIG. 10B).

The potential transport velocities in Table 7 are found at theintersection of PDF1,2 and the three cubic equations for GVF=0.2, 0.4,0.8—(PDF1,2 and x1,x2 as in FIGS. 9 and 10A). Imaginary and negativesolutions obtained analytically, are grayed out in Table 7, leaving anumber of five real and positive solutions for each PDF's value (FIG.10A).

To find the actual transport velocity Um (as a pair solutioncorresponding to the intersection with PDF1 and PDF2, the constanttransport flowrate Qm property is used (Example 1; Eqs. 21a,b,c).Qm1=Qm2; Qm1=Ak1·Um1=Ak2·Um2  Eqs. (21, a,b,c)The existing sensor feature maps (three sensor feature maps as PDF=F(Um)for GVF=0.2, 0.4 and 0.8) were extracted to illustrate the approach usedin Example 3, along with the measured PDF values as in FIG. 10A andTable 7.

Using Eqs. (21 a,b,c), an equality between the relative modification ofmetered flow areas Ak1,2 and respective transport velocities Um1,2 isillustrated by Eqs. (21a, b):

$\begin{matrix}{\lbrack {\frac{{Um}_{1}}{{Um}_{2}} = \frac{{Ak}_{2}}{{Ak}_{1}}} \rbrack_{{{at}\mspace{11mu}{GVF}},{{Um}\mspace{20mu}{SOLUTION}}}\ldots\mspace{14mu}{or}\mspace{14mu}\ldots{\quad\lbrack {\frac{{Um}_{1} - {Um}_{2}}{{Um}_{2}} = \frac{{Ak}_{2} - {Ak}_{1}}{{Ak}_{1}}} \rbrack_{{{at}\mspace{11mu}{GVF}},{{Um}\mspace{20mu}{SOLUTION}}}}} & {{Eq}.\;( {21,a,b} )}\end{matrix}$

The “pair metering operation characteristic”

$\begin{matrix}{{Cx}_{1 - 2} = {\frac{{Ak}_{2} - {Ak}_{1}}{{Ak}_{1}} \equiv \frac{D({Ak})}{{Ak}_{1}}}} & {{Eq}.\;(22)}\end{matrix}$Is used to successively test the validity of equation 21b, for allsensor feature map extracted GVF equations (it could actually be anumber in excess of 100 specific GVF's equations but for this example,only three are shown for GVF=0.2, 0.4, 0.8).

Using Eqs. (21a,b), two metering process characteristics are defined as:“Area Ratio” . . . Cx(area)=(Ak2−Ak1)/Ak1  Eq. (23)“Velocity Ratio” . . . Cx(velocity)=(Um1−Um2)/Um2  Eq. (24)

TABLE 6a Cx (“Area RATIO” as metering area ratios) based on input datapresented in Table 6 “Area RATIO” 8 Cx = (Ak2 − Ak1)/Ak1 (%) −0.4628814′ where: Ak2/Ak1 (—) 0.995371Cx value calculated as ratios of metering areas for a pair meteringoperation is a function of apparatus design, in this case indicated as“GLIMS#3”—in accordance with data in Table 6 and basic Eq 21b. Cx1-2(area) value as “Area Ratio”=−0.462881, is further compared to “VelocityRatios” obtained from Um analytical solutions of cubic (sensor feature)equations GVF=0.2, 0.4 and 0.8 for PDF1 and PDF2 (Table 7).

Table 8 is a summary of calculated “Velocity Ratios” for the pair PDF's(as PDF1,2) using the pair Um's solution values summarized in Table 7and definition equation 23. In order to find the actual Um (andimplicitly the attached GVF), a search operation is performed bycomparing the “Area Ratio with all possible “Velocity Ratios” values(Table 8) (five “potential” solutions).

TABLE 8 Summary of calculated “Velocity Ratios” GVF (Um1 − Um2)/Um2 (%)0.2 −0.681365 n/a 0.3578314 0.4 −0.462882 n/a 0.1247982 0.8 −0.570687n/a n/a

Table 9 summarizes “Velocity Ratios” (as have been illustrated by Table8) and the differential “ratios” used to find the most appropriate GVFand Um solutions. For this example limited to only three sensor featuremaps/curves and using a precise calculations (only six decimal digitsillustrated), a perfect match is obtained for GVF=0.4 (which is to beexpected—since GVF=0.4 was used in conjunction with Qm=2.78 m³/h (Table6) to create “seed” values to ultimately determine two valid PDF1,2).

TABLE 9 Comparison of calculated “Velocity Ratios” and comparison withthe target “Area Ratio” for searching the actual GVF and transportvelocity Um (Um data Table 7) Reference Area Ratio “Velocity Ratio”−0.462881 (Um1 − Um2)/Um2 (%) Differences (AR − VR)/AR GVF (—) (—) (—)GVF % % % 0.2 −0.681365 n/a 0.3578314 0.2 −47.20 n/a 177.31 0.4−0.462882 n/a 0.1247982 0.4 0.00 n/a 126.96 0.8 −0.570687 n/a n/a 0.8−23.29 n/a n/a

During actual field measurements, errors are introduced due to bothinternal (or apparatus- and procedure related) and external orfield-related conditions. Finding the actual GVF and transportedvelocity Um is subject to imposing an acceptable error value “ERR” as inEq. (25):ERR (%)<[Reference Area Ratio]−[Velocity Ratio]  Eq. (25)

-   -   (as per all Um solutions of GVF=0 . . . 1 sensor feature        equations)

Example 4

A summary of metered and calculated steps (from a deemed acceptablemetering pair x₁,x₂) follows:

1. Assess and store the PDF values (PDF1,2) measured at x₁ and x₂.

2. For (known) x₁.x₂ values and the apparatus design dimensions,calculate the relative area flow modification as:

$\begin{matrix}\lbrack \frac{{\Delta({Ak})}_{({1 - 2})}}{{Ak}_{1}} \rbrack & {{Eq}.\;(26)}\end{matrix}$3. Extract from the existing sensor feature map database all available“n” cubic equations (for GVF=0.05 . . . 0.95) and eliminate all cubicequations that have a “U-shaped” form with a known minimum value ofPDFmin for which PDFmin>PDF1, 2, as these equations will not yield asolution because PDF1 and PDF2 do not intersect the curve.4. Successively obtain all potential Um solutions (positive, real) fromequations:F(Um)_(GVF)−PDF1=0 and  (a)F(Um)_(GVF)−PDF2 and organize all 2·n solutions as in Table 7 (which,for simplicity was built for three cubic equations and six possiblesolutions only).  (b)5. Compare the relative modification of flow area (indicated as “AreaRatio” for specific example in Table 6a) with relative variation ofpotential transport velocities as obtained from 2*n extracted sensorfeature maps (indicated as “Velocity Ratio” for specific example inTable 9) subject to the acceptable accuracy given by Eq. (24).6. Assign the obtained solution (as for critical error related toapparatus and field metering conditions) to the particular GVF extractedsensor characteristic (as PDF=F(Um)GVF). Using the Um respectivesolution, calculate the actual flowrates and then convert them forstandard P,T conditions using customary accepted thermodynamic (PVT)correlations.7. Assess the solution validity and display on an external graphic userinterface.

What is claimed is:
 1. A method for determining a property of a flowingmultiphase fluid comprising the steps of: (a) directing the multiphasefluid through an apparatus comprising: a body comprising an entrance fordirecting the multiphase fluid, and an exit for discharging themultiphase fluid and defining a flow passage between the entrance andthe exit for directing the flow of the multiphase fluid therethrough;and a flow diverter assembly comprising a stationary housing disposeddownstream of the entrance; and a movable flow diverter movable towards,within, or away from the stationary housing, the stationary housing andthe movable flow diverter together defining a metering flow area andguiding the flow of the multiphase fluid towards and out of the meteringarea; (b) positioning the movable flow diverter at a home position; (c)monitoring the multiphase fluid with at least one monitoring device incommunication with the metering flow area to obtain a signalrepresenting the property of the multiphase fluid; (d) determining avalue of the property of the multiphase fluid by comparing the signalwith a set of sensor feature maps; (e) adjusting the movable flowdiverter by predetermined increments proximate to the home position toobtain a first pair of reference signals, and comparing the referencesignals with the set of sensor feature maps to determine values of theproperty of the multiphase fluid; (f) comparing the value obtained instep (d) with the values obtained in step (e); and (g) based on thecomparison, continuously monitoring the multiphase fluid, orre-adjusting the position of the movable flow diverter within or awayfrom the stationary housing to obtain a new home position and suitablemetering conditions in the metering area.
 2. The method of claim 1,wherein in step (e), the first pair of reference signals is generatedby: setting the movable flow diverter in a first position and monitoringthe fluid with the at least one monitoring device to obtain a firstreference signal representing the property of the multiphase fluid; andsetting the movable flow diverter in a second position and monitoringthe fluid with at least one monitoring device to obtain a secondreference signal representing the property of the multiphase fluid;wherein the home position is median to the first position and the secondposition.
 3. The method of claim 2, wherein in step (g), settingsuitable metering conditions in the metering area is conducted byadjusting the movable flow diverter to a new home position; monitoringthe multiphase fluid with the at least one monitoring device to obtain asignal representing the property of the multiphase fluid; anddetermining a value of the property of the multiphase fluid by comparingthe signal with a set of sensor feature maps.
 4. The method of claim 3,further comprising adjusting the movable flow diverter by incrementsproximate to the new home position to obtain a second pair of referencesignals, and comparing the reference signals with the set of sensorfeature maps to determine values of the property of the multiphasefluid.
 5. The method of claim 4, wherein the second pair of referencesignals is generated by: setting the movable flow diverter in a thirdposition and monitoring the fluid with the at least one monitoringdevice to obtain a third reference signal representing the property ofthe multiphase fluid; and setting the movable flow diverter in a fourthposition and monitoring the fluid with the at least one monitoringdevice to obtain a fourth reference signal representing the property ofthe multiphase fluid; wherein the new home position is median to thethird position and the fourth position.
 6. The method of claim 4,further comprising comparing the values obtained with the movable flowdiverter at the new home position with the values obtained from thesecond pair of reference signals; and based on the comparison,continuously monitoring the multiphase fluid, or re-adjusting theposition of the movable flow diverter within the flow passage to obtainsuitable metering conditions in the metering area.
 7. The method ofclaim 1, wherein the multiphase fluid comprises a gas phase and a liquidphase and wherein the property of the multiphase fluid to be determinedis a measure of the total transport velocity and relative proportions ofthe gas phase and the liquid phase expressed as gas void fractioncontained in the multiphase fluid.
 8. The method of claim 7, wherein thetransport velocity and gas void fraction are derived from at least, twopressure oscillation signals obtained from an acceleration transducer.9. The method of claim 8, wherein deriving the transport velocity andgas void fraction comprises the steps of: creating a set of data pointsfrom the signal; developing a set of probability density functions ofthe signal; and obtaining the value for the property from the set ofprobability density functions.
 10. The method of claim 9, wherein theprobability density function is selected from: i) the maximumprobability density value expressed as PDF_(max); ii) a difference in avalue of the PDF_(max) between transport velocities obtained from thepairs of reference positions; and iii) a derivative expressed asD(PDF)/D(x_(i)).